METHOD AND A THERMOPLASTIC FILM FOR USE IN PRINTED PACKAGING OF ABSORBENT HYGIENIC ARTICLES

Abstract

This description relates to a method for establishing the printability of a thermoplastic film for use in packaging for absorbent hygiene products, such thermoplastic film comprising at least 30% recycled polymer material. The method comprises scanning a sample of such film for Gel Spots, defining a Gel Spot Quantity and a Relative Gel Spot Coverage Area, and determining that if the Gel Spot Quantity is less than or equal to a first threshold and the Relative Coverage Area is less than or equal to a second threshold, the thermoplastic film is deemed suitable for printing. The description also relates to a method for forming packaging from a thermoplastic film and packaging comprising a thermoplastic film.

Description

METHOD AND A THERMOPLASTIC FILM FOR USE IN PRINTED PACKAGING OF ABSORBENT HYGIENE ARTICLES FIELD OF INVENTION This description relates to a method for determining the printability of a thermoplastic film for use in packaging for absorbent hygiene products, the thermoplastic film comprising at least 30% recycled polymer material. The description also relates to a method for forming packaging from a thermoplastic film, and packaging for absorbent hygiene products comprising thermoplastic film. BACKGROUND OF THE INVENTION Absorbent hygiene products, such as diapers, feminine hygiene products, incontinence products, hygiene items, toilet paper, sanitary napkins, and the like, are conventionally stored, distributed, and sold in multipacks. Some items may also be supplied in single-packs. These packages are typically disposable, meaning they are intended for single use and subsequent disposal. Such packages are typically made of or comprise a thermoplastic film. There is a desire to increase sustainability in the field of packaging for absorbent hygiene products. To this end, there is a desire to manufacture thermoplastic films for packaging at least partially from recycled polymer materials. However, a problem exists because recycled polymer materials often come from unknown sources and can include a wide variety of different polymers. Consequently, thermoplastic films produced using or containing recycled polymer materials can exhibit very different properties, depending on the recycled content of the batch used in production. To enable the use of such thermoplastic films in large-scale production, there is a need to quickly and accurately determine which thermoplastic films meet the requirements for their intended end purpose and which do not. Thermoplastic films used in packaging for absorbent hygiene products typically range from 20 to 100 microns in thickness. To be suitable for packaging, thermoplastic films must exhibit certain properties, depending on the specific packaging requirements. For example, the thermoplastic film may need to exhibit a certain degree of tensile and / or drop strength. If the thermoplastic film is to be printed before or after the formation of the packaging for absorbent hygiene products, we have identified specific considerations. If the thermoplastic film exhibits visual irregularities, the visual quality of the print on the film may be affected. Although irregularities in the thermoplastic film prior to printing might be visually recognizable, the full effect of those irregularities on the print may not be apparent until after printing has taken place. Accordingly, printed film or complete printed film packages may have to be discarded after a manual visual inspection for failing to meet aesthetic requirements. Discarding printed thermoplastic film constitutes material waste.This waste is particularly problematic since it appears only after the film has been printed. Manual inspection (e.g., using a microscope) of thermoplastic film and estimation of the number of irregularities in thermoplastic films has sometimes been carried out to assess film quality before printing. However, such methods generally yield subjective results and / or are relatively time-consuming, which is unsatisfactory when the need for film quality estimation increases due to the use of recycled material. Based on the above, there is a need to establish the suitability for printing of a thermoplastic film comprising recycled material for use in packaging for absorbent hygiene products. There is also a need for printed packaging for absorbent hygiene products, comprising recycled material, that provides satisfactory print quality. BRIEF DESCRIPTION OF THE INVENTION At least one of the above-mentioned needs is satisfied by a method for establishing the printability of a thermoplastic film for use in packaging for absorbent hygiene items, the thermoplastic film comprising at least 30% recycled polymer material, as described below. The method comprises: Provide a sample of the thermoplastic film, preferably a 10 cm x 10 cm sample; Scan the sample to provide a pixelated image of the sample; Analyze the pixelated image by computer using a thresholding method to transfer the image to a binary image in which each pixel is determined as either dark or light; Define each group of contiguous pixels as dark, like a Gel Spot, Define a Gel Spot Size for each Gel Spot that is the circular equivalent diameter for the pixel area of ​​the Gel Spot; Determine a Gel Spot Quantity indicative of the number of Gel Spots in the sample, which has a Gel Spot Size greater than or equal to 150 microns; and Determine a Relative Gel Spot Coverage Area indicative of the relative area of ​​the sample covered by Gel Spots that have a Gel Spot Size greater than or equal to 150 microns, using the equivalent circular diameter; and If the Gel Spot Quantity is less than or equal to a first threshold and the Area of ​​bcci in / cznz / e / Yi If the relative coverage of gel spots is less than or equal to a second threshold, the thermoplastic film is deemed suitable for printing; and If the Gel Spot Quantity is greater than the first threshold and / or the Relative Gel Spot Coverage Area is greater than the second threshold, determine that the thermoplastic film is not suitable for printing. In this description, the term “Gel Spot” is used to describe a visual defect in a film. Such defects may originate, for example, from non-polymeric matter in the recycled material mix (such as wood fibers, paper, or other materials), from polymer material that has a different melting temperature than the main residue, or from unfused or unevenly distributed polymer material. The term “Gel Spot” is used herein for any of these visual defects in the film, regardless of its origin. The number, size, and distribution of Gel Spots in thermoplastic film made at least partially from recycled polymer material can vary greatly depending on the material in the source of the recycled polymer material. Using the method described above, the Relative Gel Spot Coverage Area, which indicates the relative area of ​​a film sample covered by gel spots, is used to distinguish thermoplastic films suitable for printing from those unsuitable, along with the Gel Spot Quantity. The method considers gel spots to be those with a Gel Spot Size greater than or equal to 150 microns, as measured by the method described herein. The use of the method allows for the non-manual evaluation of thermoplastic films comprising at least 30% recycled polymer material, which can be evaluated before printing and thus contributes to more efficient manufacturing and induces less material waste. The method involves taking a sample of the thermoplastic film. Optionally, the sample can be a selected area from a larger sheet or roll of thermoplastic film. Alternatively, the sample can be cut from the thermoplastic film, which may be convenient as the sample can then be easily fed into a separate scanner for evaluation. The sample size can be selected to ensure that a relevant measurement of the Relative Gel Spot Coverage Area can be obtained. This may depend on the estimated distribution of the Gel Spots over the area of ​​the thermoplastic film. For example, a sample size of 10 x 10 cm may be suitable. The sample is scanned to provide a pixelated image of the sample. Scanners suitable for performing such scanning and providing the scan result in a form suitable for computer analysis are known in the field. As is known in the field, the sample can be scanned multiple times, providing multiple images, from which average values ​​can be calculated to obtain results as accurate as possible. For example, the sample bcci in / cznz / e / Yi can be scanned three times, and average values ​​can be calculated from the three scans to provide a pixelated image of the sample. The pixelation resolution must be sufficient to allow the identification of gel spots with a Gel Spot Size (as explained below) greater than or equal to 150 microns. For example, the pixelation resolution can be at least 1700 dpi (dots per inch). The pixelation resolution can also be, for example, at least 2400 dpi (dots per inch). Three scans of the sample are performed and the resulting images are combined before continuing the image analysis. The scanning equipment may introduce some brightness variation. Taking this variation into account, the pixelated image can be standardized, where a pixel value is the average of Px = ((Px-Prom(ROI)) / Std(ROI) in two perpendicular directions, see Fig. 6. The resulting pixelated image from the scan is analyzed by computer using a threshold method to provide a binary image in which it is determined whether each pixel is either dark or light. For example, the pixelated image can be analyzed by computer using a constant threshold method for grayscale. A suitable constant threshold for grayscale can be determined, for example, by comparison with reference samples that are manually evaluated for the occurrence of Gel Spots. Each group of contiguous pixels in the binary image, which appears to be dark, is defined as a Gel Spot. For example, the binary image can be formed using the light component over the RGB spectrum. For each Gel Spot, a Gel Spot Size is defined which is the equivalent circular diameter with respect to the pixel area of ​​the Gel Spot. Gel Spots with a Gel Spot Size greater than or equal to 150 microns are counted in the sample, the number of which is a determined Quantity of Gel Spots. In addition, a Relative Gel Spot Coverage Area, indicative of the relative area of ​​the sample covered by Gel Spots having a Gel Spot Size greater than or equal to 150 microns, is determined using the circular equivalent diameter. According to the method described herein, if the Gel Spot Quantity is less than or equal to a first threshold and the Relative Gel Spot Coverage Area is less than or equal to a second threshold, the thermoplastic film is determined to be suitable for printing. The first threshold indicates a limit for the number of gel spots on the film, while the second threshold indicates a limit for the proportion of the film's area covered by the gel spots. Therefore, by considering both measurements, the evaluation of thermoplastic films can be carried out. The first and second thresholds can be determined depending on the printing requirements to be applied to the thermoplastic film. For example, detailed printing, such as small printed text, may require relatively low thresholds to provide the desired print accuracy. However, for example, a large area covered by a single color might require relatively low thresholds since a gel smear on a single large colored area can stand out as very obviously detectable. To establish the thresholds, one can investigate what print quality of the packaging is perceived as acceptable by a user. In addition to the method steps mentioned above, further steps can be applied, for example, to remove sets of contiguous pixels that appear to be dark but are likely not Gel Spots. For example, the method might include a step to assess the solidity of each group of contiguous pixels identified as dark. Such a step could involve comparing the solidity of each group of contiguous pixels identified as dark to a specified solidity threshold. The method may also include, for example, removing small groups of pixels from the pixelated image before determining the Gel Spot Size and the Number of Gel Spots. For instance, only groups of pixels larger than a certain number of threshold pixels can be analyzed to determine the Gel Spot Size and the Number of Gel Spots, where this threshold number of pixels can be determined to remove groups of pixels that may never reach the Gel Spot Size limit of 150 microns or more. Optionally, the first threshold is less than or equal to 450 per 100 cm2 sample, such as less than or equal to 300 per 100 cm2 sample. Optionally, the second threshold is less than or equal to 20%, such as less than or equal to 12%. The method can be used for films with a transparency that allows scanning and discerning any gel spots. For example, the method can be used for films with an opacity of 70% or less. Optionally, the film includes color pigments embedded in the film resin. These color pigments provide a uniform color to the thermoplastic film, which would not interfere with the determination of the Gel Stains. Optionally, the film has a thickness of between 20 and 70 microns. Optionally, the film comprises less than 80% recycled polymer material. Optionally, the film includes: a. a total sum of thalates that is in the range of 0.05 to 250 mg / kg (ppm), such as 0.05 to 100 mg / kg (ppm) or such as 0.05 to 20 mg / kg (ppm), and / or b. a total sum of organotin compounds that is in the range of 0.0003 to 0.5 mg / kg (ppm), such as 0.0003 to 0.1 mg / kg (ppm) or such as 0.0003 to 0.02 mg / kg (ppm); and / or c. a total sum of heavy metals that is in the range of 0.1 to 100 mg / kg (ppm), such as 0.1 to 60 mg / kg (ppm) or 0.1 to 30 mg / kg (ppm); and / or d. a total sum of Bisphenol A that is in the range of 0.05 to 20 mg / kg (ppm), such as 0.05 to 10 mg / kg (ppm) or 0.05 to 5 mg / kg (ppm). bcci in / cznz / e / Yi The total concentrations of each chemical group, for example, phthalates, organotin compounds, heavy metals, and / or Bisphenol A, in the film, can preferably be analyzed before film formation, in the recycled resin material. Alternatively, the total concentrations of each chemical group can be analyzed in the film during production. The total concentrations of these substances are relevant to the suitability of the film for use in packaging for hygiene products. The organotin compounds include at least TBT and TPhT. The heavy metals include at least Pb, Hg, Cd, and hexavalent Cr. The phthalates include at least DINP, DEHP, DNOP, DIDP, BP, DBP, DIBP, DPHP, and DCHP (DINP = diisononyl phthalate, DEHP = di-(2-ethylhexyl) phthalate, DNOP = di-n-octyl phthalate, DIDP = diisodecyl phthalate, BBP = benzylbutyl phthalate, DBP = dibutyl phthalate, DIBP = diisobutyl phthalate, DPHP = di-(2-propylheptyl) phthalate, DCHP = dicyclohexyl phthalate). Optionally, the film is a glossy, transparent film whose opacity can be determined. Optionally, the method comprises determining the opacity of the thermoplastic film, and if the opacity is within a specified range, determining that the film is suitable for printing and for packaging absorbent hygiene products; and if the opacity is outside the specified range, determining that the film is not suitable for printing and for packaging absorbent hygiene products; where the opacity range is less than 25%, such as less than 20% or 4 to 18%. Opacity is measured as the percentage of incident light that is scattered by more than 2.5 s through the plastic film. Several factors contribute to light scattering, including impurities present in the thermoplastic film. Opacity is an additional factor that can be relevant to the film's printability. Opacity can be measured according to ASTM D1003. Optionally, the method includes: Determine an MD force at 5% elongation in the machine direction of the film; and if the MD force at 5% elongation is within a 5% elongation range, determine that the film is suitable for printing and for packaging for absorbent hygiene products, and if the MD force at 5% elongation is outside the 5% elongation range, determine that the film is not suitable for printing and for packaging for absorbent hygiene products, wherein the MD force at a 5% elongation range is greater than or equal to 3 N / 15 mm and optionally 4 to 9 N / 15 mm. Optionally, the method includes: Determine a CD force at 5% elongation in the transverse direction of the film, and if the CD force at 5% elongation is within a CD force elongation range at 5%, determine that the film is suitable for printing and for packaging for absorbent hygiene products, and if the CD force at 5% elongation is outside the CD force elongation range at 5%, determine that the film is not suitable for printing and for packaging for absorbent hygiene products, wherein the CD force at 5% elongation is greater than or equal to 3 N / 15 mm, and optionally 4 to 9 N / 15 mm. The MD and / or CD tensile strength at 5% elongation of the thermoplastic film may be relevant for its suitability in forming packaging for a hygiene product. The MD and / or CD tensile strength at 5% elongation can be determined according to DIN EN ISO 527. Optionally, the method includes: Determine a 2% CD secant coefficient in the transverse direction of the film. If the 2% CD secant coefficient is within a range of 200 to 600, determine that the film is suitable for printing and for packaging absorbent hygiene products. If the 2% CD secant coefficient is outside the range of 2% CD secant coefficient, determine that the film is not suitable for printing and for packaging absorbent hygiene products. Optionally, the method includes: Determine a 2% MD secant coefficient in the machine direction of the film, and if the 2% MD secant coefficient is within a range of 2% MD secant coefficient, determine that the film is suitable for printing and for packaging for absorbent hygiene products, and if the 2% MD secant coefficient is outside the range of 2% MD secant coefficient, determine that the film is not suitable for printing and for packaging for absorbent hygiene products, where the range of 2% MD secant coefficient is from 200 to 550. The coefficient of a material is expressed as the applied stress divided by the resulting strain, which can be visualized using a stress-strain curve. The secant coefficient at 2% represents a straight line drawn from the origin to a specific point that represents 2% on the stress-strain curve. The 2% MD and / or CD drying coefficient of the thermoplastic film may be relevant to its suitability for use as packaging for a hygiene product. The 2% MD and / or CD drying coefficient can be determined according to DIN EN ISO 527. Optionally, the method comprises determining a coefficient of kinetic friction of the film; if the coefficient of kinetic friction is within a range of coefficient of friction, determine that the film is suitable for printing and for packaging for absorbent hygiene products; and if the coefficient of kinetic friction is outside a range of coefficient of friction, determine that the film is not suitable for printing and for packaging for absorbent hygiene products, wherein the range of coefficient of friction is greater than or equal to 0.1, optionally less than or equal to 1.4, and optionally 0.1 to 0.4. The coefficient of kinetic friction can be determined according to DIN EN ISO 8295. Secondly, a method is provided for forming a packaging for absorbent articles, comprising: To provide a thermoplastic film material, determined to be suitable for printing, for use in packaging for absorbent hygiene items according to any of the options determined above; and Forming packaging for absorbent hygiene items comprising thermoplastic film. Optionally, the method also includes printing at least a portion of the film. Optionally, the packaging formation stage comprises forming a thermoplastic film package, such that the thermoplastic film forms an external surface of the package. Optionally, the packaging comprises the thermoplastic film as a co-extruded monolayer film. Optionally, the packaging formation stage includes folding the thermoplastic film to form a pocket or bag. Optionally, the method includes filling the packaging with absorbent hygienic items. Optionally, absorbent hygiene items are sanitary items, such as, for example, diapers, feminine towels, panty liners and / or incontinence products or garments. Optionally, the absorbent articles comprise absorbent tissue paper or non-woven material, such as, for example, sanitary napkins, handkerchiefs, toilet paper, or household paper. The absorbent articles may be folded, such as, for example, folded or unfolded sanitary napkins or handkerchiefs. Optionally, the absorbent articles may be rolled, such as rolls of absorbent tissue paper, for example, household paper, or toilet paper. Optionally, the absorbent items are arranged in the packaging in the form of a stack of sanitary items. Alternatively, the method comprises filling the packaging with a stack of sanitary items. Optionally, the method comprises filling the package with a single absorbent hygiene item, in order to provide a package containing only one individual item. Optionally, the individual absorbent hygiene item is a sanitary item. Optionally, the method comprises forming a variety of film packages, the variety comprising at least 1000 packages, such as at least 10000 packages. In a third aspect, packaging is provided for an absorbent article made using the method described in the second aspect. In a fourth aspect, packaging is provided for an absorbent article, comprising a thermoplastic film, wherein the thermoplastic film comprises at least 30 to 80% by weight of recycled polymers, and the thermoplastic film has a continuous unprinted area of ​​at least 10 x 10 cm, wherein the thermoplastic film has a Gel Spot Quantity that is less than or equal to 450 and a Relative Gel Spot Coverage Area that is less than or equal to 20%, as determined by the specific Gel Spot Estimation Method, described in the detailed part below, of this application. Optionally, the thermoplastic film has a printed area outside the continuous, unprinted area. Optionally, the thermoplastic film, at least in the unprinted area, is transparent. Optionally, the thermoplastic film comprises color pigment in the film resin. Optionally, the film has a thickness of between 20 and 70 microns. Optionally, the film comprises less than 80% recycled polymer material. Optionally, the film includes: a. a total sum of phthalates that is in the range of 0.05 to 250 mg / kg (ppm), such as 0.05 to 100 mg / kg (ppm) or such as 0.05 to 20 mg / kg (ppm); and / or b. a total sum of organotin compounds that is in the range of 0.0003 to 0.5 mg / kg (ppm), such as 0.0003 to 0.1 mg / kg (ppm) or such as 0.0003 to 0.02 mg / kg (ppm); and / or c. a total sum of heavy metals found in the range of 0.1 to 100 mg / kg (ppm), such as 0.1 to 60 mg / kg (ppm) or 0.1 to 30 mg / kg (ppm); and / or d. a total sum of Bisphenol A that is in the range of 0.05 to 20 mg / kg (ppm), such as 0.05 to 10 mg / kg (ppm) or 0.05 to 5 mg / kg (ppm). Optionally, the film has an opacity that is less than 25%, such as less than 20% or 4 to 18%. Optionally, the film has an MD strength at 5% elongation in the machine direction of the film, wherein the MD strength at a range of 5% elongation is greater than or equal to 3 N / 15 mm, and optionally 4 to 9 N / 15 mm. Optionally, the film has a CD strength at 5% elongation in the transverse direction of the film, which is greater than or equal to 3 N / 15 mm, and optionally 4 to 9 N / 15 mm. Optionally, the film has a 2% CD secant coefficient in the transverse direction of the film, wherein the 2% CD secant coefficient is from 200 to 600 MPa. Optionally, the film has a secant coefficient of MD at 2% in the machine direction of the film, which is from 200 to 550 MPa. Optionally, the film has a coefficient of kinetic friction that is greater than or equal to 0.1, optionally less than or equal to 0.4, and optionally 0.1 to 0.4. In a fifth aspect, a variety of at least 1000 packages is provided in accordance with the fourth aspect determined above, the packages having similar appearance and content. The characteristics, explanations, and measurement methods mentioned above in relation to one aspect of the description can be similarly applied to other aspects of the description. BRIEF DESCRIPTION OF THE FIGURES With regard to the attached figures, a more detailed description of variants of the methods and devices described herein is presented below, citing the variants as examples. Fig. 1 is a flowchart that schematically illustrates a method for establishing the printability of a thermoplastic film for use in packaging for absorbent hygiene items; Fig. 2a is an example of a scanned image of a sample of a thermoplastic film; Fig. 2b is a histogram of the distribution of Gel Spot Sizes in Fig. 2a; Fig. 3 is a flow diagram that schematically illustrates a method for forming a package of absorbent hygiene items from a thermoplastic film; Fig. 4 illustrates a variant of a package comprising an absorbent hygienic article; Fig. 5 illustrates another variant of packaging comprising an absorbent hygiene item; Fig. 6 illustrates the standardization of the scanned image. DETAILED DESCRIPTION OF THE INVENTION Figure 1 is a flowchart that schematically illustrates a method for establishing the printability of a thermoplastic film for use in packaging for absorbent hygiene items, the thermoplastic film comprising at least 30% recycled polymer material, the method comprising: Provide a sample of the thermoplastic film, preferably the sample being 10 cm x 10 cm (S100); Scan the sample to provide a pixelated image of the sample (S200); Analyze the pixelated image by computer using a threshold method to transform the image into a binary image where each pixel is considered either light or dark (S300); Define each group of contiguous pixels considered dark as a Gel Spot (S400); Define a Gel Spot Size for each Gel Spot as the circular equivalent diameter for the Gel Spot pixel area (S500); Determine a Gel Spot Quantity, indicative of the number of Gel Spots in the sample, which have a Gel Spot Size greater than or equal to 150 microns (S600); and Determine a Relative Gel Spot Coverage Area, indicative of the relative area of ​​the sample covered by Gel Spots that have a Gel Spot Size greater than or equal to 150 microns, using the equivalent circular diameter (S700); and if the Amount of Gel Spots is less than or equal to a first threshold and the Area of ​​bcci in / cznz / e / Yi If the Relative Gel Spot Coverage is less than or equal to a second threshold, determine that the thermoplastic film is suitable for printing (S800); and if the Amount of Gel Spots is greater than the first threshold and / or the Relative Gel Spot Coverage Area is greater than the second threshold, determine that the thermoplastic film is not suitable for printing (S800'). The method can use an RGB (Red Green Blue) color model for computer analysis of the pixelated image. The threshold method for transforming the image into a binary image can be a threshold method for grayscale. The following describes a specific Gel Spot Estimation Method. Although this application describes how a more general method may be used, it should be understood that the description also refers to this specific Gel Spot Estimation Method per se. In particular, the description also refers to packaging made of a film that exhibits a Gel Spot Count of less than or equal to 300, for example, less than or equal to 400, and a Relative Gel Spot Coverage Area of ​​less than or equal to 12%, for example, less than or equal to 20%, as determined by the specific Gel Spot Estimation Method.The description also refers to packaging comprising a film having an unprinted area, wherein, in the unprinted area, the film exhibits a Gel Spot Count less than or equal to 300, for example, less than or equal to 400, and a Relative Gel Spot Coverage Area less than or equal to 12%, for example, less than or equal to 20%, as determined by the specific Gel Spot Estimation Method. Description of the Gel Stain Estimation Method A sample area of ​​the film measuring 100 x 100 mm is scanned. To provide a sample of the thermoplastic film (S100), a 110 x 110 mm sample is cut from the film. A frame defining the 100 x 100 mm open area is placed over the sample to define the area to be scanned. To perform the sample scanning stage to provide a pixelated image of the sample (S200), the frame containing the sample is placed with the film side facing the scanner glass. The sample must remain flat and relaxed, without wrinkles. The scanner is then started. The scanner used is an Epson Perfection V750 Pro, with the following parameters: Document type: Film (with film side) Type of film: Positive film Image type: 24-bit color Resolution: 2400 Correction: turned off Settings: No color correction The sample is scanned three times without moving the sample or frame. The scanned images are fed into a computer, where they are analyzed by the computer as pixelated images. bcci in / cznz / e / Yi To carry out the stage of computer analysis, the pixelated image using the RGB (Red, Green, Blue) spectrum (S300), Matlab is used. Images are formed in the RGB spectrum. Initially, an average of the R, G, and B channels of the three images is taken at each pixel in order to form a combined image. A standardization of the light component of the combined image, as explained above and in relation to Fig. 6, can be carried out taking into account any brightness variation. The standardized image is then converted to a binary image where each pixel is determined to be either dark or light. All pixels above a constant grayscale threshold are classified as gel spot pixels. The constant grayscale threshold is a fixed value applied after the image has been standardized. This threshold can be determined, for example, by threshold optimization using a manually counted number of gel spots in a sample as a reference. The grayscale threshold used in this example method was -4.05. Each group of contiguous gel spot pixels is determined to be a Gel Spot. In order to define a Gel Spot Size for each Gel Spot that corresponds to the equivalent circular diameter with respect to the pixel area of ​​the Gel Spot (S500), and to determine a Number of Gel Spots, indicative of the number of Gel Spots in the sample, whose Gel Spot Size is greater than or equal to 150 microns (S600), and to determine a Relative Coverage Area of ​​Gel Spots, indicative of the relative area of ​​the sample covered by Gel Spots, which have a Gel Spot Size greater than or equal to 150 microns, using the equivalent circular diameter (S700); a Matlab function was used. The equivalent circular diameter can be calculated as the square root of (4*(Pixel Area) / pi). The equivalent circular diameter corresponds to the diameter (in miles) that the Gel Spot would have if it were in the shape of a circle with the same area as the pixel area of ​​the Gel Spot. The image was adjusted by removing small sets of contiguous pixels, using a Matlab algorithm called bwareaopen(image, p, conn), where p = size of sets to be automatically removed. P was set to 15, and conn to 4. “P” represents the size of the groups to be automatically removed and “conn” the connectivity. In addition, an assessment of the solidity of each group of contiguous pixels determined to be dark (gel spot pixels) was used to determine which groups are true gel spots. Solidity compares the pixel area of ​​a group of gel spot pixels to the area of ​​the smallest possible rectangle that could encompass the group of gel spot pixels. Solidity is defined as (geel spot pixel area) / (area of ​​the smallest possible rectangle that could encompass the group). In this case, the solidity requirement was set at 0.3; that is, a group of contiguous pixels with a solidity less than 0.3 is not considered to be a Gel Spot. The result of the Matlab computer analysis will be expressed as a quantity of bcci in / cznz / e / Yi Gel Spots and a Relative Coverage Area of ​​Gel Spots. In this example, the first threshold applied is 300 per 100 cm² of sample, and the second threshold applied is 12%. According to the above, if the Gel Spot Count is less than or equal to 300 and the Relative Gel Spot Coverage Area is less than or equal to 12%, the thermoplastic film is determined to be suitable for printing (S800). A film that is deemed suitable for printing could optionally be further evaluated with respect to the additional parameters mentioned in the brief description section above. The following sections will present various parameters measured on three different thermoplastic film samples. Sample 1 is a thermoplastic film made from virgin material and therefore contains no recycled polymer. In this case, the virgin material is polyethylene, a fossil-based polymer. Sample 1 is therefore not covered by this description but serves only as a reference for comparison. Sample 2 is a thermoplastic film comprising 33% recycled polymer (POR), with the remainder being the same virgin material as Sample 1. Sample 3 is a thermoplastic film comprising 55% recycled polymer (PCR), with the remainder being the same virgin material as Sample 1. The recycled polymer material in sample 02 and sample 03 comprises an unknown mixture of recycled polymer materials. The recycled polymer materials in sample 02 and sample 03 originate from the same recycled material sources. The three samples 01, 02, 03 are extruded single-layer films. The three samples were evaluated using the Gel Counting method described above to determine the Gel Spot Count and the Relative Gel Spot Area. Several additional parameters were also measured, as shown in the table. As can be seen in the tables below, the Gel Spot Count is less than or equal to 300, and the Relative Gel Spot Coverage Area is less than or equal to 12% for all three samples. As shown in the tables, several additional properties of the thermoplastic film materials were also measured. bcci in / cznz / e / Yi Sample % PCR Thickness (µm) MD 2% Secant Coefficient (MPa) MD 2% Secant Coefficient (MPa) 01 0 25 372 464 02 33 25 299 348 03 55 25 320 345 Sample E'CR Force elongation MD at 5% (N / 15 ητπ) Force elongation CD at 5% (N / 15 rrmj Kinetic friction coefficient (dyn) (MD) ívi) Kinetic friction coefficient (dyn) (CD) (vi! Opacity (%) Quantity Gel Spots Relative Area of ​​Gel Spots 01 0 6.3 7.8 0.33 (0.33) 0.15 (0.14) 15.5 176 7.59 02 33 5.4 5.9 0.15 (0.12) 0.14 (0.12) 10.9 134 6.38 03 55 5.7 5.9 0.18 (0.16) 0.14 (0.12) 13 144 7.16 bcc iin / cznz / e / YiAi The parameters measured, as indicated in the table above, can be compared with the desired ranges determined in the brief description section above. Accordingly, it is found that both sample 02 with 33% recycled material and sample 03 with 55% recycled material exhibit properties that make the materials suitable for printing and for use as packaging materials for hygiene products. Figures 2a and 2b are examples of a scanned image of a sample, included to illustrate the distribution of gel spots on the thermoplastic film. Figure 2a is an example of a scanned image of a thermoplastic film, in this case, one of the three images taken for sample 02. Some of the gel spots can be seen as darker spots in the image. Figure 2b is a histogram showing the distribution of gel spots in the image of Figure 2a. In this histogram, the number of gel spots with sizes in the range of 150 to 300 microns is shown in the first key element as viewed from the left, the number of gel spots with sizes in the range of 300 to 500 microns is shown in the second key element, and the number of gel spots with sizes in the range of 500 microns and larger is shown in the third key element. As can be seen from Fig. 2b, in this example histogram, the number of gel spots that are between 150 and 300 microns in size is approximately 190, the number of gel spots that are between 300 and 500 microns in size is approximately 10, and the number of gel spots that are larger than 500 microns is clearly less than 10. Accordingly, the example histogram illustrates an example where the total number of gel spots is less than 300. As indicated in the previous example of a Gel Spot Counting method, it is proposed that the first threshold in the general method be set at 300 (the number of gel spots is less than or equal to 300) and the second threshold at 12% (the relative coverage area of ​​gel spots is less than or equal to 12%). These thresholds have been found to result in acceptable print quality after visual inspection of thermoplastic films following printing. Therefore, the methods proposed here offer an advantage over previous procedures for estimating whether a thermoplastic film will be suitable for printing and for forming packaging for hygiene products. For example, such procedures could include manual estimation of the occurrence of gel spots by visual inspection of a sample of the film, for example, under a microscope.By comparison, the methods proposed here provide increased reliability and increase efficiency. Figure 3 is a schematic flow diagram of a method for forming a packaging for absorbent articles, comprising: Providing a thermoplastic film material, determined to be suitable for printing, for use in packaging for absorbent hygiene items in accordance with any of the methods described herein (S10), and Forming a packaging for absorbent hygiene items, comprising the thermoplastic film (S20). The method may involve printing at least a portion of the film, taking advantage of the fact that the film is certainly determined to be suitable for printing. The packaging can be formed by any method desired for forming packaging for absorbent hygiene items, comprising the thermoplastic film. In particular, the packaging formation stage may comprise the formation of a thermoplastic film package, such that the thermoplastic film forms an external surface of the package. Optionally, the packaging comprises the thermoplastic film as a co-extruded monolayer film. Optionally, the packaging formation step includes folding the thermoplastic film to form a pocket or bag. Additionally, the method may include filling the package with one or more absorbent hygiene items. For example, the absorbent items may be in the form of a stack of sanitary products. Figure 4 illustrates a package 1 formed from a thermoplastic film 2. The film 2 forms an exterior of the package 1, the exterior of which is at least partially provided with a print. The package 1 contains absorbent hygiene items 3, in this case, a stack of absorbent hygiene items 3. Film 2 can be printed using any conventional technique for printing thermoplastic films for the purpose of forming packaging for absorbent hygiene products. Optionally, the film can be printed using flexography. Optionally, and as illustrated in Fig. 4, the film is printed in such a way that the packaging exhibits an unprinted area 4 and a printed area 5. When the packaging 1 includes an unprinted area 4 that is at least 10x10 cm in size, the Quantity of Gel Spots and the Relative Coverage Area of ​​Gel Spots can be measured in this unprinted area 4 of the packaging. Figure 5 illustrates another package 1, formed from a thermoplastic film 2. The film 2 is folded to form a pocket-shaped package 1. In this example, the package 1 comprises a single absorbent hygiene item 3. However, it is understood that packet-shaped packages 1, as illustrated in Figure 4, or pocket-shaped packages 1, as illustrated in Figure 5, may contain a single item or a plurality of absorbent hygiene items 3. Also, a plurality of absorbent hygiene items in a single package 3 may be packaged in an outer package. In other unillustrated examples, packaging may be provided comprising absorbent articles such as absorbent tissue paper or non-woven material. Once the suitability of a thermoplastic film for printing and use in packaging for absorbent hygiene products has been established for a formed thermoplastic film, it is anticipated that no further evaluation of that thermoplastic film is necessary. Accordingly, a variety of packages can be formed from the thermoplastic film, for example, a variety comprising at least 1,000 packages, or even at least 10,000 packages. Therefore, a large number of packages can be formed where the suitability of the film for printing and for use in packaging for absorbent hygiene products does not need to be verified again. However, since the use of recycled polymer material will necessarily imply that the 15 properties of the thermoplastic film are altered each time a new source or batch of recycled polymer material is used, the printability of a thermoplastic film for use in packaging for absorbent hygiene items would need to be established for each such new source or batch.

Claims

1. A method for establishing the printability of a thermoplastic film for use in packaging for absorbent hygiene items, said thermoplastic film comprising at least 30% recycled polymer material, the method being characterized in that it comprises: - providing a sample of said thermoplastic film, preferably said sample being 10 cm x 10 cm (S100); - scanning said sample in order to provide a pixelated image of said sample (S200); - computer-analyzing said pixelated image using a thresholding method to convert the image to a binary image in which each pixel is determined as either dark or light (S300); - defining each group of contiguous pixels considered dark as a Gel Spot (S400); - defining a Gel Spot Size for each Gel Spot which is the circular equivalent diameter with respect to the pixel area of ​​the Gel Spot (S500);determine a quantity of Gel Spots, indicative of the number of Gel Spots in such a sample, which has a Gel Spot Size greater than or equal to 150 µm (S600); and determine a Relative Coverage Area of ​​Gel Spots, indicative of the relative area of ​​such a sample covered by Gel Spots having a Gel Spot Size greater than or equal to 150 µm, using such a circular equivalent diameter (S700); and if such Quantity of Gel Spots is less than or equal to a first threshold and such Relative Coverage Area of ​​Gel Spots is less than or equal to a second threshold, determine that such thermoplastic film is suitable for printing (S800); and - if such Quantity of Gel Spots is greater than such first threshold and / or such Relative Coverage Area of ​​Gel Spots is greater than such second threshold, determine that such thermoplastic film is not suitable for printing (S800).

2. The method according to claim 1, further characterized in that such first threshold is less than or equal to 450 per 100 cm2 sample, such as less than or equal to 300 per 100 cm2 sample.

3. The method according to claim 1 or 2, further characterized in that such second threshold is less than or equal to 20%, such as less than or equal to 12%.

4. The method in accordance with any of the preceding claims, further characterized in that such film comprises color pigments in the film resin.

5. The method in accordance with any of the preceding claims, further characterized in that such film has a thickness of between 20-70 µm.

6. The method in accordance with any of the preceding claims, further characterized in that such film comprises less than 80% recycled polymer material.

7. The method according to any of the preceding claims, further characterized in that such film comprises: a. a total sum of phthalates in the range of 0.05 to 250 mg / kg (ppm), such as 0.05 to 100 mg / kg (ppm) or such as 0.05 to 20 mg / kg (ppm), and / or b. a total sum of organotin compounds in the range of 0.0003 to 0.5 mg / kg (ppm), such as 0.0003 to 0.1 mg / kg (ppm) or such as 0.0003 to 0.02 mg / kg (ppm); and / or c. a total sum of heavy metals in the range of 0.1 to 100 mg / kg (ppm), such as 0.1 to 60 mg / kg (ppm) or 0.1 to 30 mg / kg (ppm); and / or d. a total sum of Bisphenol A that is in the range of 0.05 to 20 mg / kg (ppm), such as 0.05 to 10 mg / kg (ppm) or 0.05 to 5 mg / kg (ppm). bccL Ln / eznz / e / Yi 8. The method according to any of the preceding claims, further characterized in that such method comprises determining the opacity of such thermoplastic film, and if such opacity is within a certain opacity range, determining that such film is suitable for printing and for packaging hygienic absorbent products; and if such opacity is outside such opacity range, determining that such film is not suitable for printing and for packaging hygienic absorbent products; wherein such opacity range is less than 25%, such as less than 20% or 4 to 18%, and wherein the opacity is measured as the percentage of incident light that is scattered by more than 2.5° through such film.

9. The method according to any of the preceding claims, further characterized in that such method comprises: determining a force MD at 5% elongation in the machine direction of such film; and if such force MD at 5% elongation is within a range of 5% elongation, determining that such film is suitable for printing and for packaging for absorbent hygiene products; and if such force MD at 5% elongation is outside such range of 5% elongation, determining that such film is not suitable for printing and for packaging for absorbent hygiene products; wherein such force MD at a range of 5% elongation is greater than or equal to 3 N / 15 mm and optionally 4 to 9 N / 15 mm.

10. The method according to any of the preceding claims, further characterized in that such method comprises: determining a CD force at 5% elongation in the transverse direction of such film; and if such CD force at 5% elongation is within a CD force elongation range of 5%, determining that such film is suitable for printing and for packaging for hygienic absorbent products; and if such CD force at 5% elongation is outside such CD force elongation range of 5%, determining that such film is not suitable for printing and for packaging for hygienic absorbent products; wherein such CD force at a 5% elongation range is greater than or equal to 3 N / 15 mm and optionally 4 to 9 N / 15 mm.

11. The method according to any of the preceding claims, further characterized in that such method comprises: determining a 2% CD secant coefficient in the transverse direction of such film; if the 2% CD secant coefficient is within a range of 2% CD secant coefficients, determining that such film is suitable for printing and for packaging absorbent hygiene products; and if such 2% CD secant coefficient is outside such a range of 2% CD secant coefficients, determining that such film is not suitable for printing and for packaging absorbent hygiene products; wherein such a range of 2% CD secant coefficients is from 200 to 600 MPa.

12. The method according to any of the preceding claims, further characterized in that such method comprises: determining a 2% MD secant coefficient in the machine direction of such film, and if such 2% MD secant coefficient is within a range of 2% MD secant coefficients, determining that such film is suitable for printing and for packaging absorbent hygiene products; and if such 2% MD secant coefficient is outside such a range of 2% MD secant coefficients, determining that such film is not suitable for printing and for packaging absorbent hygiene products; wherein such a range of 2% MD secant coefficient is from 200 to 550 MPa.

13. A method for forming a package for absorbent articles, characterized in that it comprises: - providing a thermoplastic film material; - determining that such thermoplastic film is suitable for printing for use in a package for absorbent hygiene articles by carrying out the method according to any one of claims 1 to 12 (S10); and - forming a package for absorbent hygiene articles comprising the thermoplastic film (S20).

14. The method according to claim 13, further characterized in that it comprises: - printing at least a portion of such film.

15. The method according to claim 13 or 14, further characterized in that such step of forming a package comprises forming a package of such thermoplastic film such that such thermoplastic film forms an external surface of such package.

16. The method according to any of claims 13 to 15, further characterized in that such packaging comprises such thermoplastic film as a co-extruded monolayer film.

17. The Method according to any of claims 13 to 16, further characterized in that such packaging formation step comprises folding such thermoplastic film to form a pocket or bag.

18. The method according to any of claims 13 to 17, further characterized in that it comprises filling such packaging with absorbent hygienic articles.

19. The method according to claim 18, further characterized in that such absorbent articles are a stack of sanitary articles.

20. The method according to claim 19, further characterized in that such absorbent articles comprise absorbent tissue paper or non-woven material.

21. The method according to any of the preceding claims, further characterized in that it comprises the formation of a variety of packages of such film, such variety comprising at least 1000 packages, such as at least 10000 packages.

22. A package for an absorbent article, characterized in that it comprises a thermoplastic film comprising at least 30 to 80% by weight of recycled polymers, and such thermoplastic film having a continuous, unprinted area (4) of at least 10x10 cm, wherein such thermoplastic film has a Gel Spot Quantity that is less than or equal to 450 per 100 cm2 sample and a Relative Gel Spot Coverage Area that is less than or equal to 20%, as determined by the method as claimed in any of claims 1-12, wherein the package is made by the method as claimed in any of claims 13 to 21.

23. The packaging according to claim 22, further characterized in that, in such packaging, such thermoplastic film has a printed area (5) outside of such unprinted, continuous area.

24. The packaging according to claim 22 or 23, further characterized in that said thermoplastic film is transparent, at least in said unprinted area. bccL Ln / eznz / e / Yi 25. The packaging according to any of claims 22 to 24, further characterized in that such thermoplastic film comprises color pigment in the film resin.

26. The packaging in accordance with any of claims 22 to 25, further characterized in that it comprises an absorbent hygienic article.

27. A variety of at least 1000 packages as claimed in any of claims 22 to 26, characterized in that the packages have a similar appearance and contents.

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